Cyclone furnace



A. SIFRIN CYCLONE FURNACE Filed Dec. 27, 1950 lNVEN-lA-OR I l nd/mas `.9H/m BY @V0/M..- ATTORNEY United States Parent O CYCLONE FURNACE Andreas Sifrin, Oberhausen, Rhineland, Germany, as-

signor to The Babcock & Wilcox Company, Rocklegh,

N J., a corporation of New Jersey Application December 27, 1950, Serial No. 202,980 In Germany July 8, 1949 Public Law 619, August 23, 1954 Patent expires July 8, 1969 3 Claims. (Cl. 110-28) The present invention relates to the construction and operation of cyclone type furnaces for burning ash-con- 1 bustion air thereto.

nace chamber as a liquid slag, and more particularly L to furnaces of the character described in which the gaseous products of combustion are discharged from the furnace chamber adjacent the point of entry of the combustible mixture of fuel and air.

The granular fuels normally used in such furnaces t have particle sizes vof and under, and contain as a result of the fuel crushing operation a proportion of dust-like particles, known as fines The fueland air mixture is introduced into the combustion chamber at a high velocity througha tangential inlet arranged to effect a whirling motion of the fuel'and air mixture in a helical lpath axially of and toward the opposite end of the furnace. In' operation, the entering fuel and air stream is rapidly ignited and the centrifugal effect of the ICC 2 scriptive matter in which I have illustrated and described a preferred embodiment of my invention.

0f the drawings: l

Fig. l is a somewhat diagrammatic sectional elevation of a vertical cyclone furnace constructed in accordance with my invention, and the adjacent portion of a secondarycombustion chamber in an associated water tube steam boiler; and

Fig. 2 is a horizontal section taken on the line 2-2 of Fig. 1.

As shown in the drawings, the combustion chamber of the cyclone furnace illustrated has an upper substantially cylindrical portion 10A defined by a circular Wall 12 arranged about a ,vertical axis and having one or more tangentially arranged taperingtnozzles 14 for supplying a combustible mixture of granular fuel and primary com- The combustion chamber also includes a lower downwardly tapering truste-conical section 10a formed by a correspondingly shaped circular wall 16 extending downwardly from the wall 12 to a slag outlet 18 at the lower end thereof. At the upper end of the combustion chamber is arrangedl a concentric gas outlet 19, defined by a throat member 20 extending downwardly below the level of the combustion chamber roof and terminating at its upper end in a substantially horizontal vfloor 22 of a secondary combustion chamber 24 of an associated steam boiler. The, secondary combustion chamber licor 22 is lined with water tubes 26 which are bent aroundlthedischarge end 0f the throat member 20, to permit the discharge of 'gases fromV the cyclone furnace therebetween land to allow molten slag separated whirling stream causes the ash particles released from the ;y

burning fuel particles to deposit in a molten condition on the furnace wall and form a film orlayer of molten slag thereon on which the larger fuel particles are caught and burned. In the operation of such furnaces there is a tendency for the finer fuel particles to separate from l the main fuel and air stream and be' carried outl in an unburned condition by the slag, resulting in a loss of unburned combustibles. This would lbe particularly important in a cyclone furnace arranged about a vertical axis, and having both its fuel and air inlet and gas outlet at the upper end thereof and a slagoutlet at the lower end thereof. With such an arrangement any fuel particles falling out of the whirling stream of fuel and air are liable to be carried away in an unburned condition through the slag outlet in the bottom of the furnace chamber.

ln accordance with the present invention such unburned carbon losses are avoided or minimized in cyclone furnaces of the character described by the provision of an elongated conical extension of the furnace chamber at the end thereof opposite the gas outlet, and the introduction of a regulable supply of secondary combustion air into the furnace chamber at that end to 4aid in returning the separated fine particles to the manrcombustion zone. To avoid undesirablev cooling of the slag on the furnace chamber walls and discharging -from the slag discharge opening, the secondary combustion air is advantageously preheated by the admixture of heating gases recirculated from the furnace chamber.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and dein the secondary combustionchambertopass downwardly into the gasoutlet 19. The walls 12, 16 and 20 of the combustion chamber and gas 'outlet are lined with refractory covered water tubes'28, 30 and 32 respectively, which are connected in any suitable manner into the liuid circulation system of the associated steam boiler.

At the lower end ofthe combustion chamber section 10' is connected a conduit 36 opening to the chamber through one side of the slag outlet 18. The outer end 37 of the conduit opens to the atmosphere and a ow of secondary combustion Aair is induced therethrough and controlled by a valve 38. The described arrangement is suitable when the boilerfurnace 24 is normally operated under a sub-atmospheric pressure effected by draft producing means. If the furnace 24 is to be operated under a super-atmospheric pressure, the air inlet 37 would be connected to a suitable source of super-atmospheric air.

The `lower end of the slag outlet 18 projects within and'makes an air-tight jointwith a housing 40 of belllike form, the vertical walls of which dip into a Water pool maintained in a subjacent slag-receiving trough 42, whereby the slag outlet is sealed against the surrounding atmosphere and permitting a suction to be created on the air supply conduit 36.

In operation, the combustible mixture of primary air and granular fuel enters the annular space of the upper end of the combustion chamber at a high velocity and burns in a whirling stream flowing in a helical converging path downwardly therein. The greater portion of the incombustible ash residue from the burning fuel is deposited on the4 combustion chamber walls in a molten condition to form a sticky layer thereon and the excess slag flows downwardly on the wall 16 and through'the sealed slag outlet 18 into the trough 42. Due to the arrangement 'of -and ldraft-on the gas outlet 19 and the downwardly tapering formation of the combustion section 10', the downward flow of the whirling stream of gaseous products of combustion tends to be retarded and turns inwardly towards the axis of the combustion chamber. A whirlpool effect results, with the static pressure along the axis lower than at the periphery. The flow of secondary combustion 'air Yinduced through the air inlet 37 and "the conduit'o and "upwardly through "the combustion chamber tends to promote afsecondary gas circulation, as indicated by the arrows in Fig. 1. The `flotation effect of 'the air'an'd Vgases Yin the lower section of the 'combustion chamber prevents anyfuefneswhich 'may still 'bepresent in suspension from passing downwardly tothe slag outlet i a 18. VCombustion of the fuel lines i'srapidly completed by the ascending secondary air stream. The gaseous products of combustion ow upwardly through 'the gas outlet 19 into'th'e secondary combustion chamber 24.

A recirculating gas duct 44 is arranged 'alongside the l furnacechamber with its upper'end connected to a suitintroducing a combustible mixture of air and granular "fuelin suspension tangentially 'into said furnace chamber adjacent said gas outlet in amanner tending to cause line kstream suiciently to avoid vundesirable cooling of the j molten slag at the slag outlet 18 and on'the downwardly tapering walls 'of the combustion vchamber section 10a and -supplement the Iair in Vthe desired flotation of the descending tine fuel particles and secondary gas circulation. The valve 38'i`s 'arranged and operable to control the proportions 'of secondary air and 're'circulatedgases 'iu the conduit 36.v

While `in accordan'ce'with`tlie provisions of the statutes ,I haveiillustrated and describedherein the best form 'of fuel particles to separate downwardly therefrom and the remaining fuel particles-to burn adjacent to the circumferential wall of said furnace chamber under molten slagforming conditions, means forming an elongated conical extension of said furnace chamber at the lower end thereof and 'of :greater axial length than the remainder of said :furnace chamber, a molten slag outlet at the lower end of said furnace chamber extension, a secondary combustion air inlet opening into the lower end portion of said furnace chamber extension and arranged to provide an upward ow of air for the Vsupport and combustion of the separated fine fuelrparticles, and means 'for mixing recirculated gaseous products of combustion with said secondary combustion air prior to its entry into said furnace chamber extension to preheat the secondary combustion air.

3. Apparatus Afor burning-a slag-forming granular fuel having coarse and tine 'fuel particles under a furnace chambertemperature above the fuel ash fusion temperature which comprises a substantially cylindrical furnace chamber arranged 'with its axis-substantially vertical and having a gas outlet throat projecting into the upper end thereof, means for introducing a combustible 'mixture of air and granular fuel in suspension tangentially into said furnace chamber -around -said gas outlet throat in a manthe v,invention now ,known to me, those skilled in the art f will understand that changes maybe made in the form of theV apparatus disclos'ed'without 'departingfrom the spirit of'` the invention "covered by my claims, and that certain features of 'my invention may sometimesbe used to ada vantage withouta corresp'ondinguse of other features.

I claim:

1`. Apparatus for burning a Slag-'forming granular fuel having coarse and viineV fuel particles under a furnace chamber'temperature above the fuel ash fusion tempera- 'ture which comprises a substantially cylindrical furnace vchamber having a gas outlet throat projecting into one end thereof, means for introducing a combustible mixture of air and granular fuel insuspension tangentially into said furnace chamber around said gas outlet throat in a manner tending to cause ne fuel particles to separate therefrom and the remaining fuel particles to b urn adjacent to the circumferential wall of said furnace chamber under molten slag-forming conditions, means Yforming an elongated 'conical extension of .said furnace chamber symmetricallyarranged at theend-thereof opposite the chamberv end through which projects Vsaid-gas outlet throat, a moltenslag outlet from said furnace .chamber-having its discharge end `,sealed'from fthe atmosphere, a vsecondary combustion air linlet opening-into the Y smaller end portion of said furnacev chamber extension andproviding an axial flow of air for the combustion of the separated line .fuel particles, andlmeans for mixing recirculated gases from said furnacey chamber with said secondary combustionair prior to its entryinto said furnace chamber extension to preheat thersecondary combustion air,

2. Apparatus for burning-a slag-forming granularffuel having coarse and line .fuel particles `.under ia furnace chamber temperature .above the Vfuel ash fusion tempera. ture Whichcomprises a ,substantially .cylindrical 4furnace chamber arranged withits axisisubstantially vertical -and having ,a `Ygas outlet in the 'Upper- `.end thereof, means ,for

ner tending to causefine fuel particles toseparate downwardly therefrom and the remaining fuel particles to burn adjacentftothe circumferential wall of said furnace chamber under molten slag-forming conditions, means forming an elongated conical extension 'of said furnace chamber 'symmetrically 'arranged atth'e lower end thereof, said conical extension being of greater axial length than the remainder of'said'furnacerclarnben liquid heating tubes arranged to cool the'walls of said 'furnace chamber and i conical extension, 'a molten slag outlet at the lower end of saidlfurn'ace chamber extension Iand having its discharge end'seal'ed fromthe atmosphere, a secondary combustion air inlet opening'into the lower end portion of said furnace chamber extension and arranged to provide an axial ilow of vair upwardly therein for the support and combustion 'oflthe separated fine 'fuel particles, and means for mixing recirculated gases from the 'upper part of said furnace chamber with s'aidsecondary combustion air prior to its entry into said furnace chamber extension to preheat the secondary combustion air.

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